* gnu/services/networking.scm (<tor-configuration>, <hidden-service>):
New record types.
(tor-configuration->torrc): New procedure.
(tor-dmd-service): Use it.
(tor-hidden-service-activation): New procedure.
(tor-service-type)[extensions]: Extend ACTIVATION-SERVICE-TYPE.
[compose, extend]: New fields.
(tor-service): Use 'tor-configuration'.
(tor-hidden-service-type): New variable.
(tor-hidden-service): New procedure.